ORIGIN OF SPECIES IN NATURE. 
267 
corroborates this fact, for he says that his own cold and wet soil 
tends to make his double daffodils to become single. 
Mr. Darwin, some fifty-five years ago, noticed and described, 
in the Gardeners ’ Chronicle (1848, p. 628), some double flowered 
Gentiana Amarella, “ which grew on a very hard, dry, bare, 
chalk bank.” Similarly he found on an adjoining field of 
“ wretchedly sterile clay great numbers of . 'Ranunculus repens , 
producing half-double flowers.” He then asks the question, 
“ Is it, then, too bold a theory to suppose that all double flowers 
are first rendered, by some change in their natural condition, 
to a certain degree sterile?” When a double-flowering plant 
has this affection well fixed in its constitution, then it would 
seem that it is benefited by a rich soil; “ petalody ” having set 
in, it may affect every part of the flower—stamens first, then 
pistil or calyx, and finally the petals may be multiplied indefi¬ 
nitely, so that a flower of the double stock may contain more 
than fifty petals. 
That the petalody can be “in the blood,” so to say, is seen 
from the fact that, as no seed can be raised from a “ perfectly ” 
double stock, they can be procured from the “ single ” flowers. 
For by suppressing the anthers of flowers before they shed their 
pollen, the seeds (M. Yerlot observes) developed in the ovaries 
of these flowers produce double-flowering plants with great 
facility—viz. 60 to 70 per cent. If the anthers be not removed, 
then the percentage drops to 20 to 30 of double-flowering off¬ 
spring, the number of seed being reduced to five or six in a pod, 
which produced double-flowering plants, instead of from forty to 
fifty. 
As another influence, that of age may be mentioned. Thus, 
seed of Matthiola annua , sown immediately after being 
gathered, produced few double-flowering plants; while seed 
three to four years old produced many. Wallflowers gave 
similar results. 
Yet another fact may be mentioned which bears out the same 
contention. It is found that old, strong root-stocks of Dahlias 
produce strong growing plants, but they do not “ double ” well. 
Heavy foliage and rich colouring are, as a rule, adverse to 
doubling. 
The conclusion to be drawn from the above facts is that it is 
not a rich soil which first induces doubling, but a poor one; but 
